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b=HtKgSdgld/sMAU0TMWUVxXmACiP7N9GfW0Of1BRbGbzSS34g7jK7v3IRmCtuyNJee1/5HZ gss0bFi710U8ue5UMMbMVH9oTlIPtwa+D2lwSLa/iUnMvj7COzb/aHgMzgTBn9musCQYwB IqigDcYsGj4ZSkMSDijic+gT4Lv1CYvOCnDi9J58b5Qbu+RPsvO+W09ygTXq/tzVEL8go1 FC9jk5pS2G2q1RBN8FrdW7F0+yowMY0U53HJwT8P3Qu+v2oYZPv4e2BY79PBw91WMQrBJS +991f5x2FfBDHgCvlKbSvj9Z1TlSkWgNEY2VT0Bu6aNLP9uHGQ47T3ntEhlcvQ== Message-ID: <9dc5b470-fd98-4ce0-9196-089635c8852a@yoseli.org> Date: Mon, 2 Dec 2024 15:51:29 +0100 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 2/2] arch: m68k: Add STACKTRACE support To: Greg Ungerer , linux-m68k@lists.linux-m68k.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, Michael Schmitz , Geert Uytterhoeven References: <20241021-add-m68k-tracing-support-v1-0-0883d704525b@yoseli.org> <20241021-add-m68k-tracing-support-v1-2-0883d704525b@yoseli.org> <501c04d7-1a7d-4000-a948-e9effb281a05@yoseli.org> Content-Language: en-US From: Jean-Michel Hautbois In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-GND-Sasl: jeanmichel.hautbois@yoseli.org Hi Greg, On 02/12/2024 15:41, Greg Ungerer wrote: > Hi JM, > > On 27/11/24 21:26, Jean-Michel Hautbois wrote: >> Hi there, >> >> On 21/10/2024 11:44, Jean-Michel Hautbois wrote: >>> In order to use tracing, implement a basic arch_stack_walk() based on >>> the one in PowerPC. >>> Tested on a M54418 coldfire. >> >> Well, I said it was tested, but it was only compile tested basically. >> AFAICT now, I think it is not working as when I use wakeup_rt as a >> tracer, I don't have the stack trace: >> >> # wakeup_rt latency trace v1.1.5 on 6.12.0-10380-gb66f06337b66-dirty >> # -------------------------------------------------------------------- >> # latency: 2000 us, #18/18, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0) >> #    ----------------- >> #    | task: irq/100-enet-fe-118 (uid:0 nice:0 policy:1 rt_prio:50) >> #    ----------------- >> # >> #                    _------=> CPU# >> #                   / _-----=> irqs-off/BH-disabled >> #                  | / _----=> need-resched >> #                  || / _---=> hardirq/softirq >> #                  ||| / _--=> preempt-depth >> #                  |||| / _-=> migrate-disable >> #                  ||||| /     delay >> #  cmd     pid     |||||| time  |   caller >> #     \   /        ||||||  \    |    / >> kworker/-11        0dnh5.    0us :       11:120:R   + [000]      22: >> 98:R irq_work/0 >> kworker/-11        0dnh5.    0us : >> kworker/-11        0dnh5.    0us : 0 >> kworker/-11        0d..3.    0us : __schedule >> kworker/-11        0d..3.    0us :       11:120:R ==> [000]      22: >> 98:R irq_work/0 >> kworker/-11        0d..3.    0us : >>   telnetd-229       0Dnh4.    0us :      229:120:R   + [000]     118: >> 49:R irq/100-enet-fe >>   telnetd-229       0Dnh4.    0us : >>   telnetd-229       0Dnh4.    0us : 0 >>   telnetd-229       0D..3.    0us : __schedule >>   telnetd-229       0D..3.    0us :      229:120:R ==> [000]     118: >> 49:R irq/100-enet-fe >>   telnetd-229       0D..3.    0us : >>   telnetd-229       0dn.5.    0us :      229:120:R   + [000]     118: >> 49:R irq/100-enet-fe >>   telnetd-229       0dn.5.    0us : >>   telnetd-229       0dn.5.    0us#: 0 >>   telnetd-229       0d..3. 2000us : __schedule >>   telnetd-229       0d..3. 2000us :      229:120:R ==> [000]     118: >> 49:R irq/100-enet-fe >>   telnetd-229       0d..3. 2000us : >> >> Geert, Greg, and maybe other highly skilled m68k people, could you >> please help me with this particular function :-) ? >> >> Thanks ! >> JM >> >>> >>> Signed-off-by: Jean-Michel Hautbois >>> --- >>>   arch/m68k/Kconfig             |  5 ++++ >>>   arch/m68k/kernel/Makefile     |  1 + >>>   arch/m68k/kernel/stacktrace.c | 70 ++++++++++++++++++++++++++++++++ >>> +++++++++++ >>>   3 files changed, 76 insertions(+) >>> >>> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig >>> index >>> ab3375475721fa63418c40d4ba6ac76679ebc77d..7142f9759181a90269ae1ba9e682d331ee2ddbf6 100644 >>> --- a/arch/m68k/Kconfig >>> +++ b/arch/m68k/Kconfig >>> @@ -40,6 +40,7 @@ config M68K >>>       select UACCESS_MEMCPY if !MMU >>>       select ZONE_DMA >>>       select TRACE_IRQFLAGS_SUPPORT >>> +    select ARCH_STACKWALK >>>   config CPU_BIG_ENDIAN >>>       def_bool y >>> @@ -107,6 +108,10 @@ config BOOTINFO_PROC >>>         Say Y to export the bootinfo used to boot the kernel in a >>>         "bootinfo" file in procfs.  This is useful with kexec. >>> +config STACKTRACE_SUPPORT >>> +    bool >>> +    default y >>> + >>>   menu "Platform setup" >>>   source "arch/m68k/Kconfig.cpu" >>> diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile >>> index >>> f335bf3268a108a45bab079fbf0a1c8ead9beb71..4efe92af0b711b19cb1d5129f74e67a739e289b1 100644 >>> --- a/arch/m68k/kernel/Makefile >>> +++ b/arch/m68k/kernel/Makefile >>> @@ -31,3 +31,4 @@ obj-$(CONFIG_UBOOT)        += uboot.o >>>   obj-$(CONFIG_EARLY_PRINTK)    += early_printk.o >>> +obj-y    += stacktrace.o >>> diff --git a/arch/m68k/kernel/stacktrace.c b/arch/m68k/kernel/ >>> stacktrace.c >>> new file mode 100644 >>> index >>> 0000000000000000000000000000000000000000..06c7459373bd25b3bb3540cfe2a909259c1db3ce >>> --- /dev/null >>> +++ b/arch/m68k/kernel/stacktrace.c >>> @@ -0,0 +1,70 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> + >>> +/* >>> + * Stack trace utility functions etc. >>> + * >>> + * Copyright 2024 Jean-Michel Hautbois, Yoseli SAS. >>> + */ >>> + >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include >>> + >>> +static inline unsigned long current_stack_frame(void) >>> +{ >>> +    unsigned long sp; >>> + >>> +    asm volatile("movl %%sp, %0" : "=r"(sp)); >>> +    return sp; >>> +} > > If I am understanding what this is intended to do then this is probably > not right. > This will be returning the current stack pointer, which will almost > certainly not > be the current stack frame pointer. This will be the top of stack at the > call site, > which will be after the pushed locals and saved registers at the very > least for m68k. > > Does your kernel config have CONFIG_FRAME_POINTER enabled? > The default for m68k is usually disabled. Without this there won't be a > chain of frame pointers to follow like the code is trying to do below in > arch_stack_walk(). Thanks, I added the frame pointers support (select ARCH_WANT_FRAME_POINTERS) but this is not better. > Regards > Greg > > >>> +static inline int validate_sp(unsigned long sp, struct task_struct >>> *task) >>> +{ >>> +    unsigned long stack_start, stack_end; >>> + >>> +    if (task == current) >>> +        stack_start = (unsigned long)task_stack_page(task); >>> +    else >>> +        stack_start = (unsigned long)task->thread.esp0; >>> + >>> +    stack_end = stack_start + THREAD_SIZE; >>> + >>> +    if (sp < stack_start || sp >= stack_end) >>> +        return 0; >>> + >>> +    return 1; >>> +} >>> + >>> +void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn >>> consume_entry, void *cookie, >>> +                       struct task_struct *task, struct pt_regs *regs) >>> +{ >>> +    unsigned long sp; >>> + >>> +    if (regs && !consume_entry(cookie, regs->pc)) >>> +        return; >>> + >>> +    if (regs) >>> +        sp = (unsigned long) regs; >>> +    else if (task == current) >>> +        sp = current_stack_frame(); >>> +    else >>> +        sp = task->thread.ksp; >>> + >>> +    for (;;) { >>> +        unsigned long *stack = (unsigned long *) sp; >>> +        unsigned long newsp, ip; >>> + >>> +        if (!validate_sp(sp, task)) >>> +            return; >>> + >>> +        newsp = stack[0]; >>> +        ip = stack[1]; >>> + >>> +        if (!consume_entry(cookie, ip)) >>> +            return; >>> + >>> +        sp = newsp; >>> +    } >>> +} >>> >>